Selective Electrocatalytic Oxidation of Biomass-Derived 5-Hydroxymethylfurfural to 2,5-Diformylfuran: from Mechanistic Investigations to Catalyst Recovery.

Peter Kisszekelyi,Hakkim Vovusha,Binglin Chen,Gyorgy Szekely,Jozsef Kupai,Xianhai Zeng,Udo Schwingenschlögl,Rifan Hardian

doi:10.1002/cssc.202000453

Abstract

The catalytic transformation of bio‐derived compounds, specifically 5‐hydroxymethylfurfural (HMF), into value‐added chemicals may provide sustainable alternatives to crude oil and natural gas‐based products. HMF can be obtained from fructose and successfully converted to 2,5‐diformylfuran (DFF) by an environmentally friendly organic electrosynthesis performed in an ElectraSyn reactor, using cost‐effective and sustainable graphite (anode) and stainless‐steel (cathode) electrodes in an undivided cell, eliminating the need for conventional precious metal electrodes. In this work, the electrocatalysis of HMF is performed by using green solvents such as acetonitrile, γ‐valerolactone, as well as PolarClean, which is used in electrocatalysis for the first time. The reaction parameters and the synergistic effects of the TEMPO catalyst and 2,6‐lutidine base are explored both experimentally and through computation modeling. The molecular design and synthesis of a size‐enlarged C 3‐symmetric tris‐TEMPO catalyst are also performed to facilitate a sustainable reaction work‐up through nanofiltration. The obtained performance is then compared with those obtained by heterogeneous TEMPO alternatives recovered by using an external magnetic field and microfiltration. Results show that this new method of electrocatalytic oxidation of HMF to DFF can be achieved with excellent selectivity, good yield, and excellent catalyst recovery.

Highlights

Owing to the growing awareness of the inconvenient utilization of diminishing fossil resources, the fast-rising levels of carbon dioxide emissions, and the ever-increasing demand in energy, biomass-based chemical platforms have gained much interest
The electron transfer (ET) involving the substrate becomes a homogeneous process. The latter indirect method can mitigate over-oxidized side product formation and electrode passivation, which is essential for developing a sustainable process
The oxidation of HMF gained from fructose[25b] was investigated in a direct process by using a galvanostatic setup

Summary

Introduction

Owing to the growing awareness of the inconvenient utilization of diminishing fossil resources, the fast-rising levels of carbon dioxide emissions, and the ever-increasing demand in energy, biomass-based chemical platforms have gained much interest. In addition to direct electrolysis, N-oxyl radicals are commonly used catalysts for the indirect oxidation of primary and secondary alcohols.[17] 2,2,6,6-tetramethylpiperidinyl-N-oxyl (TEMPO) and its derivatives are common oxidants with industrial- and laboratory-scale applications.[18] Under electrochemical conditions, the formation of the active reactant from persistent organic radicals can be accomplished in the absence of chemical oxidants.[19,20] The catalyst-promoted electrooxidative synthesis of DFF in a biphasic system, using 4acetamido-TEMPO and a recyclable NaHCO3 (aq)/KI electrolyte, was demonstrated.[21]. We have demonstrated that the MCM-41-supported metal catalyst promoted the conversion of carbohydrates into HMF,[25] and here we report a TEMPO-mediated electrocatalytic oxidation method for the selective transformation of HMF into DFF (Scheme 1). A comparison of the recovery and catalytic performance of commercially available TEMPO derivatives (SiliaCAT TEMPO, TurboBeads TEMPO) and the OSN compatible Hub1-TEMPO was performed

Results and Discussion

Conclusions

Computational methods

Conflict of interest